A mountain of trash gave way in a massive garbage dump on the outskirts of Ethiopia's capital, killing at least 46 people and leaving several dozen missing, residents said, as officials vowed to relocate those who called the landfill home.

Addis Ababa city spokesperson Dagmawit Moges said most of the 46 dead were women and children, and more bodies were expected to be found in the coming hours.

It was not immediately clear what caused Saturday night's collapse at the Koshe Garbage Landfill, which buried several makeshift homes and concrete buildings. The landfill has been a dumping ground for the capital's garbage for more than 50 years.

About 150 people were there when the landslide occurred, resident Assefa Teklemahimanot told The Associated Press. Addis Ababa Mayor Diriba Kuma said 37 people had been rescued and were receiving medical treatment. Dagmawit said two had serious injuries.

Police officers are seen at the scene of a garbage landslide, as excavators aid rescue efforts, on the outskirts of the capital Addis Ababa, Ethiopia, on Sunday. (Elias Meseret/Associated Press)

Many people at the landfill had been scavenging items to make a living, but others live there because renting homes, largely built of mud and sticks, is relatively inexpensive.

An AP reporter saw four bodies taken away by ambulances after being pulled from the debris. Elderly women cried, and others stood anxiously waiting for news of loved ones. Six excavators dug through the ruins.

"My house was right inside there," said a shaken Tebeju Asres, pointing to where one of the excavators was digging in deep, black mud. "My mother and three of my sisters were there when the landslide happened. Now I don't know the fate of all of them."

Residents react at the scene of a garbage landslide. Many people at the landfill had been scavenging items to make a living, but others live there because renting homes, largely built of mud and sticks, is relatively inexpensive. (Elias Meseret/Associated Press)

The resumption of garbage dumping at the site in recent months likely caused the landslide, Assefa said. The dumping had stopped in recent years, but it resumed after farmers in a nearby restive region where a new garbage landfill complex was being built blocked dumping in their area.

Smaller collapses have occurred at Koshe — or "dirty" in the local Amharic language — in the past two years but only two or three people were killed, Assefa said.

"In the long run, we will conduct a resettling program to relocate people who live in and around the landfill," the Addis Ababa mayor said.

An excavator aids rescue efforts at the scene of a garbage landslide. Smaller collapses have occurred at Koshe — or 'dirty' in the local Amharic language — in the past two years but only two or three people were killed. (Elias Meseret/Associated Press)

Around 500 waste-pickers are believed to work at the landfill every day, sorting through the debris from the capital's estimated 4 million residents. City officials say close to 272,000 tonnes of waste are collected each year from the capital, most of it dumped at the landfill.

Since 2010, city officials have warned that the landfill was running out of room and was being closed in by nearby housing and schools.

City officials in recent years have been trying to turn the garbage into a source of clean energy with a $120 million US investment. The Koshe waste-to-energy facility, which has been under construction since 2013, is expected to generate 50 megawatts of electricity upon completion.

Ethiopia, which has one of Africa's fastest growing economies, is under a state of emergency imposed in October after several months of sometimes deadly protests demanding wider political freedoms.